Water-tube boiler.



w. SCHMIDT.

WATER TUBEBOILER.

APPUCATION HLED !AN.25, I915- Patented Jan. 18, 1916.

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WILHELM ,SCHlVIIDT, 0F WILHFEL'MSHbHE, NEAR GASSEL, GERMANY, ASSIGNOR T0 $GHMIDTSCHE HEISSDAMPF-GESELLSOHAFT1M. B. 11, 0F CASSEL-WILHELMSHQEE, GERMANY, A GOKPOMTION OF GERMANY.

VIATEB-TUBE BOILER,

To allwhom it may concern:

Be it known that I, WILHELM ScnMIn'r, a subject of the German Emperor, residing at Wilhelnishiihe, near Cassel, Germany, have invented a new and useful Improvement in Water-Tube Boilers, of which the following is a specification.

This invention relates to water-tube boilers, especially of the kind in which a plu-v rality' of lower cylinders or drums is'con- ,nected with one ormore upper cylinders or drums, the Whole being combined with two:

passe es for the combustion gust-is, one of, them eing located'at one sided the drum, 7

the other at the other side of the same.

it is old to improve the efficiency of such boilersby means of feed Water heaters, as Well as by pre-heaters for the air, and furthermore, in order to utilize the furnace gases in the highest possible degree, feed Water heater and air heater have already in the prior art been arranged in such a manner that the furnace gases act first upon the feed water heater and thenupon the air heater. If such an arrangement is to be employed in connection with boilers having a furnace gas passage at each side, then a feed Water heater and an air heater must be provided on each side of the boiler, whereby a corresponding increase of the number of the collecting vessels and of the fittings is entailed. As a consequence, such an arrangement is expensive and, in many cases,

diiiicult of inspection, and finally, consider able attention must be paidto the plant during service.

Now, in the novel combination and arrangement of parts forming the present invention, the feed water heater and the air heater are arranged not in series but parallel to one another, the arrangement being such that the feed water heater is situated in the passage at the one side of the boiler and the air heater is situated in the passage at the other side of the same. The heat still contained-in the one half part of the combustion gases coming from the furnace is thus taken up by the feed water heater, and the heat still contained in the other half part of said gases is taken up by the air heater; on the Whole, however, the cooling down of the gases in question is exactly as good as if the feed water heater and the Specification of Letters l atent.

up to noW.- The effect or efiiciency of thecombined parts is thus the same as with the before mentioned construction of boilers of the kind in question, but thearrangement is far simpler and far more accessible for inspection and furthermore the two kinds of preheaters mentioned may also be of simipper design. Also herein resides the merit thepresent invention. 4 Water tube boilers of the kind in ques- Patented Jan. 18, 1916. 1 Application and. January 25, 1915. Serial no. 4,392.

tion aroused chiefly for the generation of steam of high pressure, but Where such steam is employed, economical reasons ren-.

der it advisable to employ at the same time a high superheating, the superheating temperature being preferably increased up to the limit given by the. necessary durability of the superheater tubes, as Well as by the safety of the engine to be driven by the highly superheated highrpressure steam. These considerations make it necessary to provide for a good regulation of the superheating temperature in order to prevent an excess of it. I v

If a furnace gas passage contains, besides a superheater, also an air heater, no reliable regulation of the superheating temperature is possible, becauseconstant attention must be paid to the degree of heating of the air in the air heater ,WhlCll is acted on'by the same combustion gases that act upon the superheater also. If the quantity ofthese gases is diminished by throttling, the air .is at once less heated, which, generally, is contrary to done when the' superheater and the air heater are arranged in series. If however the air heater and the super-heater are arranged in separate passages, arranged respectively parallel with respect to the two sides of the boiler, and if the feed water heater is arranged in the passage containing the superheater, then the quantity of the combustion gases conducted through the passage containing the superheater and the feed Water heater may be changed exactly heating required and the heat not taken up by the superheater may be taken up by the feed water heater without any difiiculty arid thus a practically perfect utilization of the heat of the combustion gases is attained.

Where a water tube boiler'of the kind in" question is provided with a superheater and where this superheater is arranged at one side of the boiler, there the best arrangement with respct'to the best utilization of the heat of the 'furnace gases is, as appears from the foregoing statements, to arrange the superheater in the passage containing the feed water heater, provided, high superheating of the steam be intended. High superheating means also that the furnace gases are to leave the super-heater with a high temperature. If, for instance, in connection with thesteam ofhigh pressure, a superheating of this steam up to from 450 to 500 degrees centri'grade is demanded, the temperature of the furnace gases when leaving the superheater will be about 500 degrees C. -Coolirig down the gases to a considerably lower temperature might be attained either byineans of an unproportionally large superheating surface or by letting the. supcrheater work in accordance with the pure countercurrent principle. This latter method, however, is not applicable in the cases where-a very high superheating is required because those parts of the superheating tubes" through which the hottest steam is passing and which thus are, least cooled are at the same time those that are exposed to the hottest furnace gases, in

gree of heating, provided that the whole consequence of which those tube parts are easily burnt. .At the other boiler side, where there is no superheater but a correspond ingly largercvaporation surface, there the" temperature of the furnace-gases is consid erably 'lower; Generally, the temperature of the furnace gases isby about 100 degiees C. higher than the evaporation temperature. Suppose, the boiler is-to workwith a pressure of 40 atmosphere, then theevaporation temperature will amount to 150 degrees C. and that of the furnace gases will be about 100 C. more, or 350 C. respectively.

It is a simple known rule based upon the physical values for the specific'heat of the water, the air, and the combustion gases, that in a feed water heater the combustion gases are cooled down by 2 C. for approximately 1 degree ofheating, whereas in a preheater for air the combustion gases arev cooled down only by 1 C. for-the same devolume of said gases is conducted. through one or the other heater. The combustion gases may thus be cooled deeper by the feed water than by the air and it is thus a; matter of course that the feed water heater is arranged at that side of the boiler where the case in question, that side where the sufierthe grate should not amount to more than about 150 C. In connection with this point of view also theunavoidable variations of the combustion gas temperature render-it ad-. visable to arrange the air pre-heaterat that side of the boiler where there is no super-' heater. Every change in the condition of the fire, irrespectiveof whether the change be an intentional one or caused by the service as such, entails a change in the degree of superheating, as well as in the temperature of the furnace gases leaving the superheater. N ow, an increase in the temperature'of the furnace gases does no damage to the feed water heater, the only result being a cor responding increase of the temperature of the feed water, may be in connection with a.

partial evaporation of this water. If, how

ever, the air preheater is exposed to such hot gases, the temperature of the air might be so raised that the grate bars would be no more sufficiently cooled. This danger'is considerably less at the other side of the boiler,

since the temperature of the water-tubes and of the water withinthem remains approxi mately the same and the variations of the temperature of the waste gases leaving the feed water heater are thus, at this side of the l boiler, less than at the'other side.

It, the service is carried through with steam of a lower pressure and a lower superheating temperature, then it is, of course,

not of particular importanceat which side of the boiler the feed Waterheater and the air heater are arranged. The boiler in question is, of course, able to produce also such kind of steam but generally a rather high pressure and a rather high su'perheating temperature should be attained and maintained.

My invention will be better understood 5 by referring to'the accompanying drawing i-n.which- Figure l is a vertical section through one embodiment of a boiler constructedaccording to my invention, and Fig. 2 is a vertical longitudinal section through the upper feed water drum and one of the upper boiler drums, in combination with some of the pipes'connecting these two drums.

This form of construction of a water tube boiler of the kind in question is specially suited for vessels, but may be employed also in stationary plants.

Referring to said figures, the steamboiler proper consists of the two upper drums g and it, the two lower drums and in, and

m is situated between the drums 2' and k.

0, p and g designate the parts constituting the feed water heater, 0 being the upper drum of the same, the lower drum, and g the tubes. Between the tubes g of the feed water heater and the left-hand set of the tubes Z of the steam boiler proper is arranged the superheater n, this latter and the feed water heater being thus located at one side of the boiler, in the same passage, whereas the other side of the boiler is furnished with the air heater '0, which is situ ated opposite to the feed water heater. The left-hand set of the water tubes Z is considerably smaller than the right-hand set, first in order to afford the necessary space for the reception of the superheater and, second, in order to abstract considerably less heat from the fire gases streaming forth from this side of the grate for the purpose of having correspondingly more heat at dis posal for the superheater.

The cold water is introduced at 6 into the lower drum p ofthe feed water heater and the steam produced is taken off the boiler from the upper drum 0 at a. This drum is connected by pipes 1' and s with the upper drum g of the boiler proper, as well as with the upper drum h of the same, the

pipes 9* serving for conductin the hot feed water from the drum 0 to andmto the drums g and 7b and the pipes s'serving for conducting the steam from these drums to the drum 0. Owing to these objects of said pipes, the pipes 1' extend somewhat down into the drums g and 7t and the pipes 8 extend some-j what up into the drum 0, and over these upwardly pro ecting ends of the pipes 8 1s a l'mhc plate s also located within the drum 0 and serving for catching up the water carricd by means of, and with, the steam from the drums 7 and h to and into the drum 0.

Of course, othermeans than a bathe-plate may be provided for separating the water from the steam. Atany rate, the possibility of water lug carried upward by the steam within the tubes 3 is but small, as these tubes are rather narrow. The steam escaping at u ccuulucted, of course, through the pipes constitutin the su aerheater whence itis led to the engine in order to drive the seine. I wish it to be understood that the steam need not necessarily be taken off the drum 0 but it may be takenofi the drums g and it, these drums being then connected with the superheater.

Thereare provided, left-hand and righthand from the drum 0, dampers w and as,

serving for regulating the flow of the furnace gases through the left-hand and through the right-hand half of the boiler.

In other words: the damper w serves for regulating the flow of the furnace gases around the tubes of the superheater and of the feed water heater whereas the damper w is intended solely for the regulation of the flow of the furnace gases through the air heater. The air is made to pass through this heater preferably in opposite direction to the furnace gases. It is obvious that the more the damper w is opened and the damper it closed, the larger will be the quantity of the furnace gases acting upon the superheater, as well as upon the feed water heater, but if the position of the dampers 'w and a: is the reverse, then an approximately larger volume of the furnace gases will pass through the air heater. The dampers inquestion are, of course, adjusted with proper consideration to the effects to be attained, as already explained in the first part of thepresent specification.

Having now described my invention, I claim:

'In a water tube boiler, in combination with a pair of lower drums and an upper drum, two sets of water tubes connecting the lowerdrums with the upper drum one set being smaller than the other set, a flue laterally of each set of Water tubes, a feed water heater in the l'lue adjacent to the witnesses. I

, WILHELM SCHMIDT. Witnesses:

Jumps FRANKE, .GUSTAV TAUBE. 

